Research Studies on Stratospheric and Tropospheric Ozone

By: Staff Reporter
Studies show that ozone pollution is harmful for crop production while ozone depletion is damaging for aquatic ecosystems. Emission of ozone depleting CFC-11 is on the rise in Eastern Asia.

Stratospheric ozone

Arctic Ozone Depletion and Impact on Climate Change
A study which examined the Arctic ozone depletion at eight stations in the Arctic stipulates that the Arctic stratospheric ozone recovery, predicted for the mid 2030s, might be significantly delayed (Pommereau, 2018). The study observed that the 2015-2016 ozone depletion is the third largest reported since the introduction of Systèmed’Analyse par Observation Zénithale (SAOZ) network measurements in 1990. The earlier largest ozone losses were observed in 1996 and a record loss in 2010-2011. The same study shows that there will be further cooling of the Arctic lower stratosphere due to increasing greenhouse gas concentrations. There is a possibility that the return dates of ozone to pre-depletion 1980 level might be pushed back by an estimated 5-17 years than those presented in the 2014 Ozone Assessment.

Trichlorofluoromethane (CFC-11) Emissions on the Rise
In a clear violation of the Montreal Protocol of 1987, emissions of the ozone depleting trichlorofluoromethane (CFC-11) have increased in recent years despite a global ban on production. According to a paper published in Nature emission rates are similar to what they were 20 years ago and likely emanate from Eastern Asia though the exact country has not been identified (Montzka, 2018). According to official records the global production of CFC-11 was almost negligible after 2007. It was the largest contributor to the decline in atmospheric chlorine between 2007 and 2012. What is alarming is that emissions have increased by 25 per cent since 2012.

Ozone Depletion Affects Aquatic Ecosystems
Ozone depletion and climate change in aquatic ecosystems has rendered inland and oceanic water bodies vulnerable to UV radiation (Williamson, 2019). Thanks to the Montreal Protocol stratospheric ozone depletion has been reduced bringing down the effect of UV radiation on aquatic life. However the thickness of ice and duration of snow and ice cover have already been reduced, thus exposing aquatic organisms to UV radiation. Heavy precipitation and melting of glaciers and permafrost has led to ‘browning’ of waters, leading to loss of valuable ecosystem. UV radiation promotes microplastic pollutant formation and adversely affects aquatic ecosystems.

Ozone Sensitivity Studies via CCMI-1 Simulations not Consistent
10 Chemistry-Climate Model Initiative 1 (CCMI-1) models used to study the sensitivities of ozone to changes in greenhouse gases and other ozone-depleting substances showed varying data in the troposphere, upper troposphere-lower troposphere (UTLS) region and the mesosphere (Morgenstern, 2018). Data regarding the middle stratosphere was more consistent. Quantitative differences were noticed regarding the impact of total column ozone (TCO) and the impact of stratospheric ozone depletion in surface ozone. The disagreement between the CCMI-1 models also meant that the response of surface ozone to global warming remains highly inconclusive from the study.

Tropospheric ozone

Urban Greenery may Contribute to Ozone Formation
Urban green infrastructure or planting of trees is widely considered to be an effective means to improve air quality and build resilience against climate change. However, a paper published in Frontiers in Forests and Global Change claims that well-intentioned but indiscriminate planting of trees without considering the species of trees planted might contribute to ground level ozone or tropospheric ozone concentration (Fitzky, 2019). Newly planted tree species in urban areas must emit low or no BVOCs (biogenic volatile organic compounds) which are precursors to tropospheric ozone. They should also have strong resistance to natural disasters like flood and drought, large leaf area and high photosynthetic capacity.

Develop Suitable Crop Models to Simulate Ozone Damage
Development of crop growth models is necessary to understand better the effect of ozone on crops and how they interact with other environmental and global change factors. A study published by Lisa D. Emberson et al. (2018), claims that hourly or daily data revealing ozone and meteorological conditions over the course of the crop growing season will help provide details of yield, ideally compared against a low ozone control. The ozone risk assessment experimental and modeling community should be connected with Agricultural Model Intercomparison and Improvement Project (AgMIP) to allow a comparison of different models of assessment.

Ozone Pollution Affects Global Wheat Production
Ozone pollution has brought down the production of wheat by 9.4 per cent between 2010 and 2012. Gina. E. Mills et al (2018)., carried out a study in North America, Asia and Europe which showed that 85 teragrams or 24.2 billion dollars worth of wheat is lost every year because of ozone pollution. As the consumption of wheat grows, unless ozone pollution is brought under control the UN Sustainable Development Goal 2 of securing food supplies and ending hunger by 2030 might not be realised. The greatest yield losses were noticed in the warm-temperate-moist, tropical-moist and tropical-wet climates of the Northern Hemisphere and tropical-moist and –wet climates of the Southern Hemisphere.

Ozone-Poor Air in the Tropical Tropopause Layer
Data from research aircraft and ozonesondes over the West Pacific warm pool showed the generation of layers with very low ozone concentration just below the tropopause (Newton, 2018). A two month long study of data focusing on the tropical tropopause layer (TTL) presented between February and March 2014 confirmed that these layers have very low ozone concentration due to uplift by deep convection. Very low concentration of ozone in TTL was seen in both the Northern and Southern Hemisphere. Further, they provide a route for short-lived halocarbon species to reach the stratosphere. Evidence from the aircraft showed a negative correlation between ozone and species of marine origin.

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